Service discovery

Inquiry is followed by service discovery, which is based on the Service Discovery Protocol (SDP)

Your application will have a particular UUID that you have associated with it. An UUID is needed in the service discovery process. The following snippet of code helps to illustrate this.

// UUID for this service: 
String uuidString = "50FDB90ADBFB49b3AA71D6BA308E45F3"; 
String params = "; // set optional parameters as needed 
// an RFCOMM (BTSPP) based service: 
String url = "btspp://localhost:" + uuidString + params; 
try 
{ 
     StreamConnectionNotifier connectionNotifier = 
         (StreamConnectionNotifier) Connector.open(url); 
     StreamConnection connection = 
         (StreamConnection) connectionNotifier.acceptAndOpen(); 
} 
// send or receive messages to remote peer, etc.

A remote peer discovers the service by doing a service discovery on one or more found devices using the method searchServices in class DiscoveryAgent:

public int searchServices(int[] attrSet, 
                          UUID[] uuidSet, 
                          RemoteDevice btDev, 
                          DiscoveryListener discListener) 
    throws BluetoothStateException

The input parameters of the method are the set of service attributes to be retrieved for matching services, the set of UUIDs that define a matching service, the device of interest for service discovery, and a listener for handling the appropriate discovery callbacks.

An application normally performs service discovery on each found device of interest. The Java APIs For Bluetooth (JSR-82) allow multiple simultaneous service discovery transactions. The maximum number of concurrent service discoveries allowed is defined by the property “bluetooth.sd.trans.max” (see JSR-82 specification). An appropriate BluetoothStateException will be thrown if the application attempts to start more service discovery transactions than allowed. JSR-82 does not specify how the underlying implementation performs such transactions (for example, concurrently or sequentially). For related information on Nokia devices, see Games Over Bluetooth: Recommendations To Game Developers.

Service discovery callbacks are made to an appropriate listener. The listener implements the DiscoveryListener interface, which defines callback methods servicesDiscovered and serviceSearchCompleted.

© Nokia 2008.